External display for mid-2010 21.5" iMac?

[foonon]

I have a mid-2010 21.5" iMac with a bad display (diag LED 4 is off) that I don't want to fix. Everything else about it is fine.

I've been using an external monitor with a miniDP to HDMI adapter and that seems to work alright, most of the time.

Sometimes, though, when I power it on, the external display looks like everything is A-okay (it POSTs, shows the Apple logo, and I can see the boot progress bar), but I am then dropped into a light grey, blank screen with the mouse pointer. No login screen is shown.

I need to press the iMac's power button "just so" and the external display screen goes black and then the login window is visible.

Why is this happening? Any way to make it just use the external display properly all the time without manual intervention?

~f

 

[Nguyen Duc Hieu]

I have a mid-2010 21.5" iMac with a bad display (diag LED 4 is off) that I don't want to fix. Everything else about it is fine.

I've been using an external monitor with a miniDP to HDMI adapter and that seems to work alright, most of the time.

Sometimes, though, when I power it on, the external display looks like everything is A-okay (it POSTs, shows the Apple logo, and I can see the boot progress bar), but I am then dropped into a light grey, blank screen with the mouse pointer. No login screen is shown.

I need to press the iMac's power button "just so" and the external display screen goes black and then the login window is visible.

Why is this happening? Any way to make it just use the external display properly all the time without manual intervention?

~f

If the broken LCD panel is still connected to the iMac logicboard, then sometime it's still recognized by your iMac and set it as the main display (with login screen).
If that is the case, then disconnecting all cable to the LCD panel may remind your iMac that the external display is the only display it has..

 

[foonon]

The main display cable is disconnected (I think the problem is the connector on the board, not the display panel itself)

I'll see about unplugging the power and vertical hold, too, but I think I want to keep the temperature monitor cable plugged in. I recall the fans going nuts the last time I left it unplugged.

~f

 

[Nguyen Duc Hieu]

The main display cable is disconnected (I think the problem is the connector on the board, not the display panel itself)

I'll see about unplugging the power and vertical hold, too, but I think I want to keep the temperature monitor cable plugged in. I recall the fans going nuts the last time I left it unplugged.

~f

You can move the sensor head from the back of the LCD panel to any place on the aluminum case.